This invention relates to pneumatic clutches, and particularly to a pneumatic clutch havng a flexible gland which is actuated to engage and to disengage the clutch.
Pneumatic clutches which have an inflatable rubber or elastomer gland to connect rotating parts are commonly used in marine propulsion systems to control the fore and astern direction of travel of the ship. In such clutches an annular gland is typically permanently connected about the outer perimeter of an annual clutch member connected to the prime mover. The outer peripheral surface of the gland typically mounts replaceable clutch wear elements such as friction shoes. When the gland is inflated from a source of air under pressure, the shoes are moved radially outwardly to engage the inner periphery of a second annular clutch element which is connected through a drive train to the propellers. When the clutch is thus engaged, power is transmitted from the prime mover to the propellers. To disengage the clutch, the air pressure is removed and the gland is allowed to deflate.
Because of the effect of centrifugal force acting on the gland and the friction shoes, there is a tendancy of the shoes to engage the mating surface of the outer clutch element even when the gland has not been inflated. It is undesirable to allow the shoes to drag across the surface of the clutch element when the clutch should be disengaged. Therefore, some means for positively disengaging the shoes from the mating element is often required. Most typically, positive disengagement is accomplished by providing springs which retract the shoes when the air pressure is removed. An example of this approach is found in U.S. Pat. No. 2,331,180 issued Oct. 5, 1943 to Gasser. As the speed of operation of the clutch increases heavier springs are needed for disengagement. Thus, when springs are used for disengagement it may be necessary to change the springs to accommodate different applications of the clutch.
The purpose of my invention is to provide a pneumatic clutch, and a flexible gland for such clutch, in which air pressure is used to prevent engagement of the clutch as well as to engage the clutch.